The red circle shows the point in space the rod butt is being rotated about during the cast.
I drag the rod forward at the beginning of the cast with little or no rotation so the I.C. is way behind me. It then travels below the shoulder and moves out near the elbow near the MRF point.
Rotation is not dominated by the wrist rotation until near the end of the cast.
You can see my hand path angle is much less than Chris's since I do use as much shoulder rotation. Making better use of the shoulder is something for me to work on.